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International Calendar
The use of the term “ISO” in the title and body of this article is not meant to suggest or imply any formal approval or recommendation of proposals presented herein by the International Organization for Standardization (ISO). It is meant simply to signify that the proposals are compatible with ISO 8601. A modest way to propose calendar reforms are incremental, backwards-compatible additions to the international standard ISO 8601. Several such enhancements are possible, some of which are furthermore compatible (supersets) with alternate calendar proposals. Guidelines * The extended format becomes the standard format, the'' basic format'' is a condensed or collapsed version thereof. * Do not add ambiguous formats. * Only add a redundant format if there are very good reasons for it. * Collapse everything or nothing. * Support condensed format where possible. ** Do not condense formats with a one-digt part, except when it is the last one and follows an alphabetic marker. (This is suggestion that this page does not yet adhere to.) ** Disallow condensed format with plus or minus sign before year. * Do not support two-digit years in new formats, but consider their existence. ** Assume centuries for two digits in isolation. * Extend existing schemes and conventions. * ** Apply week of year determination rule to months, quarters etc. ** Reuse the ‘W’ convention for other entities if necessary. * Do not break week cycle. * Stay with 97/400 leap year cycle. * Partial values on the lright may be left out which specifies less specific dates. * Partial values on the left may be left out without dropping separators and markers. Missing parts are implied (usually using the live value). ** Separators may be dropped if markers alone make the format unambiguous. * Single alphabetic letters in a format are called “markers”. * Do not support years with more than ten digits which is already more than than the age of the universe. Existing formats From here on, the identifier ±CCYY refers to any of the three 4-digit formats above. — ±4 Note that implied century was possible in ISO 8601:2000, but this truncated format was removed in the third edition, ISO 8601:2004. For backwards compatibility, YYYYMM instead of YYMMDD is invalid, and ±YYYYMM (with leading plus or minus sign) could be confused with six-digit years ±YYYYYY. Seven-digit and eight-digit years would be ambiguous with the condensed ±YYYYDDD ordinal dates and ±YYYYMMDD full dates, respectively, therefore compact formats are only valid without a leading plus or minus sign (unless they contain a marker). Note, that the deprecated YYDDD is already compatible with five-digit years. General clarifications, additions or enhancements Large years * '-'''C+CCYY — -5, -6, -7, … * '+'C+CCYY — +5, +6, +7, … Require long format, i.e. with hyphens, because 6-, 7- and 8-digit years would be ambiguous with compact formats ±''CCYYMM, ±''CCYYDDD'' and ±''CCYYMMDD'', respectively, 5 digits (i.e. almost all of human history) are safe. Four-digit years should not have a preceding plus sign. Week-based additions : CCYY'M' is the same as CCYY'W'. The week year used herein has exactly 52 weeks (364 days) in a short year or 53 weeks (371 days) in a long year as opposed to the month year without ‘W’ marker which has 365 days in a common year or 366 days in a leap year. The term normal year is ambiguous, as it means a short year in the context of week years and a common year in the context of month years. Other * D: Sunday = 7 = 0 of following week ** 2012-W30-7 = 2012-W31-0 * W'''WW: leap week = W53 = W00 of following year Moon: 13 months : Alphanumeric dates : ‘M’ marker The week year is divided into 13 months, called '''moons. A normal moon has 4 complete weeks (28 days). The last moon in long years his a long moon and has 5 weeks (35 days). Since there is a leap week instead of intercalary days, these moons align with the week year, not the month year. This format is compatible with the New Earth Calendar. Quart: 13-week quarters : Alphanumeric dates : ‘Q’ marker : condensed variant should be avoided Each of the 4 quarters, called quarts, has 13 weeks excatly, except for the final one in long years. This long quart has 14 weeks then. Although there is no consensus on how quarts of 91 days or 13 weeks should be separated into 3 months of almost equal length, there are just two basic approaches: one divides each quarter into portions of 30 days twice and 31 days once, the other uses 4 weeks twice and 5 weeks once. Choosing the former, the Common-Civil-Calendar-and-Time calendar, the ISO-Uncia Leap Week Calendar and the Edwards perpetual calendar all use 30:30:31 days, the Symmetry010 Calendar uses 30:31:30 days and the Aristean Calendar uses 31:30:30 days. When the “Thursday rule” is applied to any of these patterns it always results in a week layout of 4:5:4 as in the Symmetry454 Calendar, i.e. neither 5:4:4 as in the Bonavian Civil Calendar nor 4:4:5. Months of quarts, furthermore, cannot match exactly the full-week months determined by the week date ('-'''MM'-W'W or '-'Q'-'M'-W'W), because the first triad may have just 12 weeks and the third triad may also have 14 weeks (like the fourth). Quarts are therefore divided into three months that primarily consists of 4, 5 and 4 weeks ('-Q'Q'-'M'-W'W'-'D) and, matching that middle-high scheme, alternatively they consist of 30, 31 and 30 days ('-Q'Q'-'M'-'DD). Without weeks or days provided, i.e. in the form '-Q'Q'-'M, there is no distinction between these – the ''month duality. There is no way to reference a day in 28|35-day months without its week. Month-based additions and clarifications Triad: 3-month quarters Three consecutive months make one of four triads. They are 90 (91 with Feb29), 91, 92 and 92 days long, respectively, and align with the common year, not with week dates. These should not be subdivided into weeks. The condensed format without hyphens is not supported with these dates, because they would collide with existing ones. Week of month or of triad The number of weeks per month, hence triads, is determined by the usual Thursday rule, that means a week belongs to the month (or triad) the majority of its days (4 to 7) fall into. A short month has 4 weeks, a long month has 5 weeks. There are 4 long months in normal years and 5 ones in 53-week long years. The term normal month'is only used for Gregorian months of 28 to 31 days. A month has 5 weeks if it has at least 29 days and starts on Thursday, has at least 30 days and starts on Wednesday, or has 31 days and starts on Tuesday. The resulting pattern is irregular. The first triad may have just 12 weeks ('short triad), the second always has 13 weeks (normal triad) and either the third or the fourth may, instead of 13, have 14 weeks (long triad). Note that triads and normal months divided into full weeks together effectively constitute the week year and not the month year. To put it differently: every date with a ‘W’ marker in it uses the week year. Financial and administrative additions Fiscal quarters, months and year : Alphanumeric dates : ‘F’ marker Each fiscal month has exactly 30 days, hence the fiscal year 360 days. (Optionally, month F13 contains 5 days, month F00 only exists in leap years and contains only 1 day.) Each of the four fiscal quarters in a year by default has 90 days in it. All start and end dates, hence exact lengths, may be user-defined. The week is not used with this format! It is not (yet) defined how this fiscal year is mapped to either a month year or a week year, because it would require intercalary days or flexible days longer than 24 hours. Academic year, semester, trimester/term under contruction Astronomic and astrologic additions Lunar year and months : Alphanumeric dates : ‘L’ marker A lunar month has 29 or 30 days and is astronomically defined. A lunar month belongs to the Gregorian year the majority of its days (15 to 30) fall into. The lunar year therefore contains 12 or 13 complete lunar months. Astronomic year and seasons, astrologic signs : Alphanumeric dates : ‘S’ marker – although ‘A’ would be possible, too. Seasons (on the Northern hemisphere): * winter = S0 = S4 * spring = S1 * summer = S2 * autumn = S3 “Taurus” for instance is “S12” or “S1-2” and neither “S02” (second sign in astrologic year) nor “S04” (fourth sign starting in a calendar year) nor “S05” (fifth sign in a calendar year). Only digits 0 through 4 are used with this format. Time Allow decimal time of day without ‘T’ prefix: “.5” and “,5” mean 12:00:00. Furthermore, allow spreadsheet-compatible date-times with 1900-01-01 epoch: * D*'.'''d* — ., 1., .1, 1.1, 2., .2, 2.1, 1.2, 2.2 … * '-'D*'.d* — -., -1., -.1, -1.1, … * '+'D*.d* — +., +1., +.1, +1.1, … Spans and periods '''under contruction * ‘Q’ is added for the 13- or 14-week quart, 3-month triads remain “3M” * ‘F’ is added for the 30-day month (“30D”). * ‘L’ is added for the lunar month (ca. 29.5 days). It should only be used with absolute start or end date. Holidays With a calendar reform there are always several ways to determine the date of annual holidays and birthdays. * Convert from the classic calendar each year, e.g. Christmas, December 25, stays at -12-25 and can fall on any day of the week. ** A special case are astronomically defined holidays which use features that are not accurately represented in the calendar, e.g. four days after the winter solstice (could be written -S0-1-04 or -S4-04 etc.). They have to be determined by observation or, rather, by independent calculation. * Convert the original date to the new calendar, e.g. 0000-12-25 was a Monday, hence -W52-1. * Use a similar looking date in the new calendar, e.g. -M12-25 which is a Thursday and equals -M12-W4-4. * Reinterpret the date in the new calendar, e.g. three weeks and four days into the last month of the year, -12-W3-4 (Thursday), or one week before the last day of the year, -W51-7 (Sunday). Depending on the reason for a holiday one or several of these methods may make sense to use. Note that stakeholders may prefer different approaches for external reasons, workers may prefer to have holidays not fall on weekends, for example. Astronomically defined holidays can of course be fixed arbitrarily in any calendar. The date of Easter in non-orthodox churches, for instance, is currently specified as the first Sunday after the first full moon after the begin of spring in the Gregorian calendar (-03-21). One could instead use the corresponding week from the year Jesus of Nazareth supposedly died on the cross, or one selects the day that is most frequently selected by the current rule or is closest to the median, -W14-7. Category:Leap Week Calendars Category:Proposed calendars Category:Equal-quarter calendars Category:28-35-day month calendars Category:30-31-day month calendars Category:28-day month calendars Category:13-month calendars